The present invention relates to electric motors, and more particularly to the assembly of electric motor components into housings designed to contain and positionally locate the motor components.
A wide variety of electrical products include internal components that generate significant amounts of heat during normal use. Prominent examples include personal computers, and components of computer systems such as servers and work stations. Frequently these devices incorporate electric motor driven fans, preferably contained in aerodynamically designed housings to more effectively move air across heat generating components and exhaust the heated air to maintain a satisfactory operating temperature. Given the strong consumer and user preferences for lower cost and smaller size, manufacturers are continually challenged to provide smaller yet equally reliable fans and motors while decreasing manufacturing costs. To this end, some manufacturers have introduced plastic housings to augment or replace previously used metal housings for the motor components. Although this has the potential to significantly reduce costs, the approach increases the difficulty of reliably securing the motor stator against axial and rotational movement.
One of these concerns arises due to the interface between the cylindrical stator body, i.e. the lamination stack, and the slight incline or truncated conical shape of an otherwise cylindrical plastic housing, present due to the draft angle required when molding the plastic part. One approach to this problem involves fixturing the stator and securing the stator with potting compound or glue. Other designs employ screws or other fasteners to retain the stator. These approaches require added time and labor, and raise process control difficulties in terms of repeatable, consistent stator positioning. Alternatively, a motor already secured within a metal casing can be mounted within a plastic housing. This entails unwanted redundancy and adds to the cost.
Therefore, the present invention has several aspects directed to one or more of the following objects:                (i) to provide a rotor mounting device with a housing and rotor retainer incorporating features that inherently guide a rotor towards centering as it is inserted into and secured within the housing;        (ii) to provide a rotor containment and fixation device that requires no auxiliary fasteners or fixturing of the rotor;        (iii) to provide a process for assembling a motor into a motor housing that requires less time and labor yet affords a more reliable and consistent positioning of the rotor and other motor components; and        (iv) to provide an improved aerodynamic configuration of a housing containing and positioning electric motor components.        